Cardiopulmonary resuscitation (CPR) is a well-known technique for increasing the chance for survival from cardiac arrest. However, it is very difficult to perform manual cardiopulmonary resuscitation with consistent high quality. Since CPR quality is key for survival there is a strong drive to have a mechanical automated device to replace less reliable and long duration manual chest compressions. Automated CPR (A-CPR) apparatuses were introduced in the market recently.
Some A-CPR systems use a pneumatic actuator mechanism while other A-CPR systems are driven by an electrical motor such as a servo motor. An A-CPR system typically comprises a backboard and an A-CPR unit having a mechanical heart-stimulator such as a compression pad, and possibly respiratory aid or electrodes for electrical resuscitation. During use, a patient is placed on the backboard, back down, and the A-CPR-unit is attached to the backboard. When doing so, it is important to transfer the force provided by mechanical heart-stimulator from the A-CPR-unit to the patient's sternum in a controlled but still forceful way.
Document WO 2010/049861 A1 discloses one such A-CPR system with an A-CPR-unit connectable to a backboard and a transmission system to control movement of a compression element. The transmission system comprises an electrical motor/gearbox combination and a transmission pulley to transfer power to two sliders that repetitively move back and forth over a guiding rail. The movement of the two sliders results in a back and forth vertical motion of the compression element to perform resuscitation. The translational motion of the sliders is obtained by changing the direction of the motor.
The electrical motor may be placed in a vertical way within the ACPR device. This option is cumbersome. For small system size, the motor/gearbox combination may be placed in the horizontal direction, so that the output shaft of the motor/gearbox is parallel to the horizontal plane and the direction of rotational motion of the pulley makes a 90 degree angle with the translation in the horizontal direction. A 90 degree angle has to be made.
Mechanisms to transfer power in a right (90 degree) angle are known. For example, a 90 degree gearbox consists of an input and output shaft that are connected by a ring and pinion or a spiral bevel gear and pinion. However, such 90 degree gearboxes have to be sufficiently large to transfer the high required moments if significant forces have to be transferred, leading to cumbersome gearboxes. Further disadvantages relate to its low efficiency and the amount of noise and vibration as the gears move along each.
Another way to transfer power over a 90 degree angle is by using a timing belt or a chain running over sprocket that is driven by a driving pulley and makes a 90 degree turn by two guide pulleys. The belt has to be twisted to make the 90 degree angle. To overcome twist the distance between pulleys has to be large. Instead of belts, ropes in both the continuous and multiple drive systems have been contemplated.
It would be desirable to have an automatic CPR system with a system for converting movement from horizontal motion into the vertical plane.
It would be further desirable to have a system for transferring power in a right angle, while maintaining low cost, high endurance and low noise.